The electromagnetic assembly is a key component in the power electronic system. The high-power reactor and transformer have been widely used in the power compensation, the power quality improvement, the frequency control, and the power equipment such as wind power and solar inverter. The electromagnetic assembly has the main function of isolating, limiting short-circuit current, var compensation, and smoothing wave.
In the operating period, the electromagnetic assembly will consume some power, which is converted into heat. The cooling to the electromagnetic assembly is required for the normal operation thereof. The common methods for cooling the electromagnetic assemblies are divided into the air-cooling mode and the liquid-cooling mode, and the electromagnetic assembly is correspondingly divided into the air-cooling electromagnetic assembly and the liquid-cooling electromagnetic assembly.
In the liquid-cooling electromagnetic assembly, the liquid-cooling plate is provided in a specific position, and the heat is removed through the circular flow of the liquid inside the liquid-cooling plate. In the liquid-cooling mode, the circular liquid tank, the circular pump, the heat exchanger and the connecting pipe are required outside the liquid-cooling plate. At the same time, a plurality of connectors in the liquid-circulation loop may tend to shorten the system life or damage the personal safety due to leakage. Thus, the entire cooling system has the disadvantages of structure complexity, large volume, high energy consumption, low reliability, high cost and so on. Further, the liquid-cooling plate is arranged between the adjacent layers of the coil and between the coil and the iron core, where a strong alternating magnetic field often exists, this may cause the eddy current loss in the liquid-cooling plate itself, resulting in additional loss, and reducing the efficiency of the electromagnetic assembly.
In the air-cooling electromagnetic assembly such as reactor or transformer, the insulated supports are provided between the iron core and coil, between the coil layers or inside the coil to define the air channel. The cold air enters from one end of the air channel and moves along the axial direction of the coil, and is transformed into the hot air through the heat exchange with the wall surface of the air channel. After that, the hot air is blown from the other end of the air channel to achieve the cooling of the electromagnetic assembly. The air-cooling mode has disadvantages that the heat exchange coefficient is low, the heat exchange area is difficult to enlarge due to dependence on the air channel surface area, and the cooling efficiency thus is low. In many cases, the conventional cooling method is unable to meet the cooling demand of the high-power electromagnetic assembly. The size and cost of the electromagnetic assembly often have to increase to meet the cooling demand.
Accordingly, it is desired to develop a high-power electromagnetic assembly of low cost and high cooling efficiency.